AlBr3-Promoted stereoselective anti-hydroarylation of the acetylene bond in 3-arylpropynenitriles by electron-rich arenes: synthesis of 3,3-diarylpropenenitriles.

Yelizaveta Gorbunova,Aleksander V Vasilyev,Dmitry S Ryabukhin

doi:10.3762/bjoc.17.180

Abstract

Reactions of 3-arylpropynenitriles (ArC≡CCN) with electron-rich arenes (Ar′H, benzene and its polymethylated derivatives) under the action of aluminum bromide (AlBr3, 6 equiv) at room temperature for 0.5–2 h result in the stereoselective formation of 3,3-diarylpropenenitriles (Ar(Ar′)C=CHCN) in yields of 20–64%, as products of mainly anti-hydroarylation of the acetylene bond. The obtained 3,3-diarylpropenenitriles in triflic acid CF3SO3H (TfOH) at room temperature for 1 h are cyclized into 3-arylindenones in yields of 55–70%.

Highlights

Conjugated acetylene nitriles are versatile building blocks in organic synthesis for the preparation of a plethora of functionalized compounds and heterocycles
We have shown that reactions of 3-arylpropenenitriles with arenes (Ar′H) under the superelectrophilic activation by the Brønsted super
It was found that acetylene nitriles 1a–c reacted with arenes in the presence of excess AlBr3 (6 equiv) at room temperature for 0.5–2 h to afford E,Z-3,3-diarylpropenenitriles 2a–o as products of the regioselective hydroarylation of the acetylene bond (Scheme 1)

Summary

Introduction

Conjugated acetylene nitriles (propynenitriles, R–C≡C–C≡N) are versatile building blocks in organic synthesis for the preparation of a plethora of functionalized compounds and heterocycles. Propynenitriles take part in electrophilic [1,2] and nucleophilic [3,4,5,6] addition reactions onto the acetylene bond leading to various substituted nitriles. Reactions onto both acetylene and nitrile groups are widely used for the construction of various heterocyclic systems [7,8,9,10,11,12,13,14,15].

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